Influence of thermal damage and the interruption time on the optical properties of InGaN quantum wall structures

Abstract

The influence of thermal degradation and the interruption time on the optical characteristics of InGaN multi-quantum-well (MQW) structures was examined. A series of 5-period In0.08Ga0.92N/In0.02Ga0.98N MQW samples with different final temperatures before cooling-down and with different interruption times during QW growth were grown on sapphire substrates by using metalorganic chemical vapor deposition. We carried out temperature-dependant photoluminescence (PL) and PL excitation measurements to elucidate the quantum efficiency and the origin of the emission, respectively. From a comparison of PL spectra and luminescence efficiency, we conclude that (1) high temperature ramping-up and exposure steps degrade the optical properties of QWs by thermal damage, (2) the InGaN QWs can be protected from thermal damage by a GaN capping layer, and (3) the interruption time during the QW growth somewhat degrades the optical properties of QWs.